IPCC Climate Change Data: CSIRO B1a Model: 2020 Mean Temperature

The CSIRO Atmospheric Research Mark 2b climate model (Hirst
et al., 1996, 1999) has recently been used for a number of more
sophisticated climate change simulations. These start from 1880
to avoid the "cold start problem". This version of
the CSIRO model includes the Gent-McWilliams mixing scheme in
the ocean and shows greatly reduced climate drift relative to
earlier versions (e.g. Dix and Hunt, 1998). The drift in global
mean surface temperature in the new control run is about -0.02
degrees C/century. Note that the model uses flux correction.
The model atmosphere has 9 levels in the vertical and horizontal
resolution of spectral R21 (approximately 5.6 by 3.2 degrees).
The ocean model has the same horizontal resolution with 21
levels. The equilibrium sensitivity to doubled CO2 of a mixed
layer ocean version of the model is 4.3 degrees. This is at the
high end of the range of model sensitivities (e.g. IPCC 1995,
Table 6.3). In the basic greenhouse gas experiment the model
combines the effect of all radiatively active trace gases into
an "equivalent" CO2 concentration. Observed
concentrations are used from 1880 to 1990 and the IS92a
projections into the future. This gives close to a 1%/year
compounding increase of equivalent CO2. Another model
experiment includes the negative radiative forcing from
atmospheric sulphate aerosol. The direct aerosol forcing is
included via a perturbation of the surface albedo, similarly to
the Hadley Centre experiments described by Mitchell et al (1995)
and Mitchell and Johns (1997) . The sulphate concentrations are
the same as used in the Hadley Centre experiments. However the
chosen aerosol optical properties are different, giving a
present day forcing due to anthropogenic sulphate of about -0.4
W/m^2. This can be compared to the 1880-1990 greenhouse gas
forcing of about 2 W/m^2. The magnitude of the 20th century
warming in the model including aerosol matches the observed
reasonably well. However there are a number of forcings missing
from the model, including solar variability, sulphate indirect
effect and the effect of soot. The climate sensitivity of
CSIRO-Mk2 is about 4.3 degrees C (Watterson et al.,1997). The central elements of the B1 future are a high level of
environmental and social consciousness combined with a globally
coherent approach to sustainable development. A strong welfare
net prevents social exclusion on the basis of poverty. However,
counter-currents may develop and in some places people may not
conform to the main social and environmental intentions of the
mainstream in this scenario family. Particular effort is devoted
to increasing resource efficiency. Comprehensive incentive
systems, combined with advances in international institutions,
permit the rapid diffusion of cleaner technology. R and D to
this end is also enhanced together with education and capacity
building for clean and equitable development. Organizational
measures are adopted to reduce material wastage, maximizing
reuse and recycling. The combination of technical and
organizational change yields high levels of material and energy
saving as well as reductions in pollution. Labor productivity
also improves as a byproduct of these efforts. Variants
considered within the B1 family of scenarios include different
rates of GDP growth and dematerialization (e.g., energy
intensity declines). The demographic transition to low mortality
and fertility occurs at the same rate as in A1 but for slightly
different reasons, motivated partly by social and environmental
concerns. Global population reaches nine billion by 2050 and
declines to about seven billion by 2100. This is a world with
high levels of economic activity and significant and deliberate
progress toward international and national income equality.
Global income per capita in 2050 averages US$13,000; somewhat
lower than in A1. A higher proportion of this income is spent on
services rather than on material goods, and on quality rather
than quantity, because of less emphasis on material goods and
also higher resource prices. The B1 storyline sees a relatively
smooth transition to alternative energy systems as conventional
oil resources decline. There is extensive use of conventional
and unconventional gas as the cleanest fossil resource during
the transition, but the major push is towards post fossil
technologies driven in large part by environmental concerns.
Given the high environmental consciousness and institutional
effectiveness in the B1 storyline, environmental quality is
high, as most potentially negative environmental aspects of
rapid development are anticipated and dealt with effectively
locally, nationally, and internationally. For example,
transboundary air pollution (acid rain) is basically eliminated
in the long-term. Land-use is carefully managed to counteract
the impacts of activities potentially damaging to the
environment. Cities are compact and designed for public and
non-motorized transport, with suburban developments tightly
controlled. Strong incentives for low-input, low-impact
agriculture along with maintenance of large areas of wilderness
contribute to high food prices with much lower levels of meat
consumption than those in A1. These proactive local and regional
environmental measures and policies also lead to relatively low
GHG emissions even in the absence of explicit interventions
directed at mitigating climate change.